You can also read the "Solving problems" section in the Application help (Help menu).

User name and password

The password requested at launch is not a serial number!You must use an administrator user name and its password (see System Preferences > Users & Groups).Note: With Mac OS X 10.7 and OS X 10.8, the applications work only if you set a password. Even if you are the only one using your computer, not setting a password is a security risk and can be very dangerous. Remember that you are connecting to the Internet!

Allow the application to access your Mac

macOS may prompt you to allow the application to control your Mac. Indeed, the application runs scripts and uses system commands that require this permission. The application will not access your personal data (in Contacts, Calendar, Reminders, and so on). If you refuse the prompt's request, the application will not work.
More info

Uninstall

To uninstall an application, open it, go in the Help menu, and choose Uninstall [application name]. In the confirmation message that appears, click the Continue button. The application and the components created while installing and using it will be removed. Empty the trash to complete the operation.